This proposal emphasizes the combined efforts and talents of a number of investigators to study the effects of drugs of abuse on the behavior of rhesus monkeys. A unique opportunity is available to conduct such a study using enclosed social groups of monkeys in a colony at La Parguera, Puerto Rico. The specific objective of the project is to study the effects of delta 9 tetrahydrocannabinol, an active constituent of marijuana, on the social and sexual behavior of semi-free ranging rhesus monkeys. The effects of chronic administration of the drug on the monkey itself and on how it affects its social and sexual interactions with other members of the social group is being studied. This research on marijuana may result in the development of a model design for examining the influence of other drugs of abuse on the social system of a non-human primate.